The principal replication strategies of viruses making use of reverse transcription. While orthoretroviruses are RNA viruses, which replicate through a DNA intermediate and require integration for reproduction, hepadnaviruses are DNA viruses replicating through an RNA intermediate without the integration of their genome. FVs appear to functionally bridge these pathways, since they reverse transcribe (at least to a significant extent) late in replication (like hepadnaviruses) and must integrate their genome into the host cell genome (like orthoretroviruses). Furthermore, cellular exit of FV particles depends on their cognate glycoprotein as in hepadnaviruses, while budding of orthoretroviral particles is Env-independent (Figure adapted from [3]). RT, reverse transcriptase.
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